Electrical resistance



June '19, 1934. E. D. 'MEAD ELECTRICAL RESISTANCE Filed Dec. 15, 1951FIG.6

A TTORNEV Patented June 19, 1934 ELECTRICAL RESISTANCE Edward D. Mead,Caldwell, N. J., assignor to Bell Telephone Laboratories,

Incorporated,

New York, N. Y., a corporation of New York Application December 15,1931, Serial No. 581,084

4 Claims.

This invention relates to electrical resistance devices and morespecifically to a type of resistance used in telephone switchboards. Thetype now in use is disclosed in Patent 1,677,240, dated July 17, 1928 toF. S. Kochendorfer et al in which a resistance wire is wound around aflat core made of partially cured phenolized asbestos to form a coil, anumber of sheets of the same material being each treated to soften thematerial to permit it to be wrapped around the coil in overlappingrelation where they are held by U shaped metal strips after a secondheat treatment in a mold under pressure. This type of construction isexpensive to manufacture.

The object of this invention is to improve and simplify the constructionof such resistance devices and to lower the manufacturing cost thereof.

According to this invention a pair of punched terminals are embedded inan elongated core of molded insulated material and around the core iswound a resistance wire to form the coil. The core has a substantiallyoval cross-section to prevent slack of the wire occurring on the sidesof the core and at the same time permitting to exert a minimum amount oftension when winding the wire around the core which thus prevents thebreaking of the wire. On the core proper is wrapped, or otherwiseapplied, a coating of insulating yieldable material to serve as acushion for the resistance wire in order to prevent the breaking of thewire due to humidity swelling the core. Reenforcing portions areprovided at both ends of the core, one serving as a base for the coreand the other portion serving for the protection of the winding in thehandling of the resistance. Both ends of the terminals extend beyond thebase of the core for soldering with the wires of the associated circuitand the other ends of the terminals protrude through the front end ofthe core for the purpose of connecting a testing apparatus whenever itis desired to 'test the resistance, the terminals being provided withlugs which protrude through the surface of the core proper for attachingthe ends of the resistance wires to the terminals and the base of thecore is provided with astud embedded therein for securing the resistanceon its mounting bar, which, in turn, is mounted on a suitable framework.

In the drawing, Fig. 1 is a side assembly view of the resistance withportions of the core and wire coverings cut away;

Fig. 2 is a cross-sectional view taken approximately on line 22 of Fig.1;

Fig. 3 is a cross-sectional view taken approximately on line 3-3 of Fig.1;

Fig. 4 is an end view;

Fig. 5 is a side view of the resistance shown in Fig. 1 modified; 1

Fig. 6 is a cross-sectional view taken approximately on line 6-6 of Fig.5;

Fig. 7 is a cross-sectional view taken approximately on line 77 of Fig.5 showing the core, the resistance wire andits insulated covering brokenaway; and

Fig. 8 is an end view of Fig. 5.

In the drawing 10 indicates a core of molded insulating material, suchas bakelite, in which the terminals 11 and 12 are embedded. The core 10is provided with a base portion 14 through which the ends of theterminals 11 and. 12 protrude as shown in Fig. 1. In the base 14 isembedded a screw threaded stud 16 engaged by a nut screw 18 for securingthe core on a mounting such as 17, the base 14 being provided withprojections 36 and 19 which engage similarly sized apertures in thesupport 17 for locating and holding the core in its adjusted position onits support upon the tightening of nut screw 18 on stud 16 and there- 39by preventing the terminals from'contacting with the support.

The core 10 is made of oval cross-section and is provided with acovering 22 of insulating yieldable material, such as cellulose acetate,to serve as a 35 cushion for the resistance wire 23 wound there on, theouter surface of the coil being, in turn, coated with an insulatingvarnish 24 as shown in Figs. 1, 2 and 3. I The terminal 12 is providedwith a lug 25 adjacent the base 14 which protrudes through the surfaceof the core and of covering 22 for connecting one end of the resistancewire 23 to this terminal. Similarly, the terminal 11 is provided with alug 26 for connecting the other end of the resistance wire 23 at thefront end of the core. The other end portions 20 and 21 of terminals 11and 12 protrude through the enlarged portion 15 .of the front end of thecore for the purpose of ;connecting a testing apparatus whenever it isdesired to test the resistance, a projection 15 being provided for theprotection of these terminals at this end of the core.

In the core 10 of the modification shown in Fig. 5 is embedded a thirdterminal 28 having a plurality of lugs 29 which extend into arectangularly shaped opening 27 in the core 10 and on this core aremounted, in the manner described in connection with Fig. 1, a pluralityof resistance coils 30 and 31. Coil 30 has one end connected to lug 25of terminal 12 and its other end to a lug 29 of terminal 28 as bysoldering. Similarly, coil 31 has one of its ends connected to a lug 29and its other end connected to lug 26 or" terminal 11, thus makingpossible a winding of a plurality of resistances on a single core. Theend of terminal 28 which protrudes through the base 14 is screw threadedfor receiving the nut screw 18 for securing the resistance on support 17and the other end of this terminal extends into a depression 35 in theend 15 of the core for the purpose of testing either of the resistancecoils, the return side of the electrical circuit being through terminal12 for the coil 30 and through terminal 11 for the coil 31.

In this resistance the oval cross-section of the core effectivelyprevents slack of the wire occurring on its sides while at the same timepermitting to exert a minimum amount of tension when winding the wirearound the core, which thus prevents the breaking of the wire and thecovering of yieldable material between the core and the windingeffectively prevents the breaking of the wire due to humidity swellingthe core.

What is claimed is:

l. A resistance device comprising a solid molded core having terminalsmolded therein and projecting from both ends, a layer of celluloseacetate covering said core, a resistance wire wound on said core insuperposed relation to said covering, said core having formed therewithan enlarged portion serving as a. base for mounting the resistancedevice on a support and a securing element molded in said enlargedportion between the projecting terminals.

2. A resistance device comprising a solid molded oval core havingterminals molded therein and projecting from both ends, a layer ofyieldable material covering said core, a resistance wire wound on saidcore in superposed relation to said covering, said core having formedtherewith an enlarged portion serving as a base for mounting theresistance device on a support, and a securing element molded in saidenlarged portion between the projecting terminals.

3. A resistance device comprising a solid molded core having terminalsmolded thereinand projecting from both ends, a layer of yieldablematerial covering said core, a resistance wire wound on said core insuperposed relation to said covering, said core having formed therewithan enlarged portion serving as a base for mounting the resistance deviceon a support, and a third terminal formed with a securing element moldedin said core between said first named terminals and projecting throughthe ends of said core and having lugs projecting through an opening inthe middle of said core to provide for connection of an intermediatepart of the wire thereto.

4. A resistance device comprising a solid molded core having terminalsmolded therein and projecting from both ends, a layer of yieldablematerial covering said core, a resistance wire wound on said core insuperposed relation to said covering, said core having formed therewithan enlarged portion serving as a base for mounting the resistance deviceon a support, a third terminal molded in said core between said firstnamed terminals and projecting through the ends of said core and havinglugs projecting through an opening in the middle of said core to providefor connection of an intermediate part of the wire thereto, saidadditional terminal be- 1 ing formed with a screw threaded portion toreceive a clamping nut for securing the device to a support.

EDWARD D. MEAD.

